Folsom v. Dewey was a United States Supreme Court case that addressed the issue of whether a state court had the authority to issue a writ of habeas corpus to a prisoner held in a federal prison. The case arose when a prisoner, Folsom, was held in a federal prison in California and sought a writ of habeas corpus from the state court. The state court granted the writ, and the federal government appealed the decision to the Supreme Court. The Supreme Court held that the state court did not have the authority to issue the writ of habeas corpus. The Court reasoned that the writ of habeas corpus was a federal prerogative, and that the state court did not have the authority to interfere with the federal government's power to imprison individuals. The Court also noted that the writ of habeas corpus was a fundamental right, and that the state court should not be allowed to interfere with the federal government's power to protect this right. The Court's decision in Folsom v. Dewey established that the state court did not have the authority to issue a writ of habeas corpus to a prisoner held in a federal prison. This decision has been cited in numerous subsequent cases, and has been used to support the idea that the federal government has the power to protect the fundamental right of habeas corpus.

In Folsom v. Dewey, the Supreme Court was tasked with determining whether a contract between two parties could be enforced when one of the parties had died before it was executed. The majority opinion held that such contracts were not enforceable because they lacked consideration and mutuality of obligation; however, Justice Field dissented from this decision. He argued that although there may have been no consideration for the deceased party to enter into the contract, their estate should still be bound by its terms since they had accepted them prior to death. Furthermore, he noted that if these types of contracts were deemed unenforceable then it would lead to an unjust result in which creditors would suffer losses due to circumstances beyond their control. Therefore, Justice Field concluded that such contracts should be recognized as valid and binding on both parties even after one has passed away.